Funds are sought to purchase an instrument to facilitate analysis of radioactive materials after fractionation by electrophoresis or chromatography. Although autoradiography has for many years been the method of choice to quantitate Southerns, Northerns, Westerns, and chromatograms, X-ray films suffer from poor sensitivity and limited dynamic range. Recent advances in other technologies now make alternatives attractive, because their use can cut exposure times significantly and provide more accurate quantitation. Among the several competing technologies we have tested, the best in terms of versatility, performance , and adaptability for use by many investigators is the Molecular Dynamics PhosphorImager. In our experience, use of this machine not only improves efficiency by reducing the time wasted while waiting for gels, blots, and chromatograms to be exposed, but the precise quantitation of the PhosphorImager opens up possibilities for new assays and applications that would otherwise be overly cumbersome or too imprecise.